US3591451A - Pretreatment of vegetable matter and delignification of the refined matter with chloring dioxide - Google Patents

Pretreatment of vegetable matter and delignification of the refined matter with chloring dioxide Download PDF

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US3591451A
US3591451A US797209A US3591451DA US3591451A US 3591451 A US3591451 A US 3591451A US 797209 A US797209 A US 797209A US 3591451D A US3591451D A US 3591451DA US 3591451 A US3591451 A US 3591451A
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chlorine dioxide
pretreatment
percent
pulp
yield
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Harry D Wilder
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Ethyl Corp
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Ethyl Corp
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    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/12—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds
    • D21C9/14—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds with ClO2 or chlorites
    • D21C9/142—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds with ClO2 or chlorites with ClO2/Cl2 in a multistage process involving ClO2/Cl2 exclusively

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  • Vegetable materials such as wood, reed, bamboo, cane and the like which are or can be used for the preparation of fibrous materials are composed of several basic parts.
  • fibrous vegetable matter is made up of about 15 to 30 percent lignins and extractives, such as resins and the like, with the remainder of the about 70 to 80 percent being carbohydrates.
  • the carbohydrate portion of the fibrous vegetable matter is about to 30 percent hemicellulose with the remainder being cellulose, and the cellulose portion of the carbohydrate is about 45 to 55 percent alpha cellulose and about 5 percent other celluloses, all percentages being expressed on a wood basis.
  • one of the first steps in conventionally converting fibrous vegetable materials to fibers for use in the preparation of paper or paper-like materials is a pulping process.
  • the primary goal of the process is to remove most of the lignins from the fibrous vegetable material and separate the remaining carbohydrate fibers into individual fibers.
  • pulping processes such as kraft, sulfite and others
  • when efforts are made to remove substantially all of the lignin from the vegetable fiber mass a major part of the hemicellulose is lost, and the remaining cellulose and hemicellulose fibers are chemically and/ or mechanically damaged.
  • the normal yield known in the art is about 45 percent by weight. But, if only the lignins and extractives were removed from the fibrous vegetable material, the yield obtained would be 70-80 percent.
  • the pulping process removes substantially only lignins and extractives from fibrous vegetable materials and leaves the cellulose and hemicellulose part of the material substantially undamaged, thereby resulting in pulp and paper products having new and unusual properties and exceptionally high strengths. Since the pulping process is reasonably selective and substantially only the lignins and extractives are removed, yields are exceptionally high and in the 55 to percent range.
  • the pulping process includes a basic sequential unit of a chlorine dioxide treatment, caustic extraction and a chlorine dioxide treatment, and this basic unit is preceded by a chemical or mechanical pretreatment of prepared vegetable fiber chips. Each step of the basic sequential unit is followed by a water washing, which may be with process liquids obtained elsewhere in the process, as by countercurrent washing which has attendant conservation ad vantages.
  • a more preferred embodiment of the process is one including a chemical and/or mechanical pretreatment of prepared vegetable fiber chips followed by the sequential processing of the pretreated chips in a chlorine dioxide treatment, a caustic extraction, a chlorine dioxide treatment, a caustic extraction and a final chlorine dioxide treatment.
  • a Water Washing or its equivalent follows each chlorine dioxide treatment and each caustic extraction.
  • An even more preferred embodiment of the process is one in which the water wash for the final chlorine dioxide treatment is used as the water wash for the preceding caustic extraction and so on countercurrently to the flow of fiber material through the process to the first water wash following the first chlorine dioxide treatment; from this point the Wash water may then be sent to waste or treated for recovery of chemicals contained therein.
  • Another preferred embodiment of the process involves the chemical pretreatment of prepared vegetable fiber chips followed sequentially by a chlorine dioxide treatment, a caustic extraction, a chlorine dioxide treatment, a caustic extraction and a final chlorine dioxide treatment with countercurrent water washing and extraction after each treatment; the most preferred chemical pretreatment is a neutral sulfite pretreatment at a specified concentration of chemicals and cooking cycle.
  • the pulp produced by the process of the present invention has a higher degree of polymerization, a higher hemicellulose content, a higher carboxyl content, and a lower carbonyl content than conventionally bleached kraft pulp from the same Wood mixture.
  • it requires less energy to refine than a conventionally bleached kraft pulp from the same wood mixture.
  • laboratory handsheets prepared from the pulp have superior tensile strength and tear strength when compared to sheets of conventionally bleached kraft pulp from the same wood mixture.
  • the above pulp properties relate directly to paper made from the pulp.
  • Such paper has higher tensile, tear, burst, fold, pick, and delamination strengths.
  • FIGS. 1 to 3 are block diagrams and FIGS. 4 to 13 are graphs.
  • FIG. 1 describes the basic process of this invention.
  • FIG. 2 shows a more preferred embodiment of the process of this invention, and
  • FIG. 3 discloses a highly preferred chemical pretreatment step for the process of this invention.
  • FIG. 4 compares yield of pretreated material with caustic utilized in each stage.
  • FIG. 5 compares G.E. brightness with caustic utilized in each stage.
  • FIG. 6 compares percent rejects with caustic utilized.
  • FIG. 7 shows final yield compared with pretreatment yield.
  • FIG. 8 compares chlorine dioxide consumption with pretreatment yield.
  • FIG. 9 shows a com parison of freeness with heating time.
  • FIG. 10 compares Schopper fold with effect of cation treatment.
  • FIG. 11 provides a comparison of MIT fold with Schopper fold.
  • FIG. 12. relates to Schopper fold to days of aging, and, FIG. 13 relates Schopper fold to years of aging.
  • fiber chips of any fibrous vegetable matter are fed first to a pretreatment step which may be either mechanical, chemical or a combination thereof.
  • the pretreated chips are then fed to a first chlorine dioxide treatment 11 where they are contacted with chlorine dioxide in either aqueous solution or as a gas.
  • the chlorine dioxide treated material is washed with water 12 to return the mixture to substantially neutral pH; following washing, the washed chlorine dioxide treated material is subjected to caustic extraction 13 for a period of about one-half to one hour.
  • the extracted material is washed again with water to return to substantially neutral pH, as indicated at 14, and to remove the water soluble materials produced in the extraction step.
  • Prepared vegetable fiber chips are fed to a pretreatment step where they are subjected to a chemical, mechanical or a combined chemical-mechanical pretreatment to make the lignin and extractives more readily available for removal.
  • the pretreated material is subjected sequentially to a chlorine dioxide treatment 21, water washing 22, caustic extraction 23, water washing 24, chlorine dioxide treatment 25, water washing 26, caustic extraction 27, water washing 28, chlorine dioxide treatment 29, and water washing 30.
  • fresh water is fed only to the last water washing by line and then circulated countercurrently to the flow of the material through the process as indicated by line 41 to the next to last water washing step 28, and from there as indicated by line 42 to the next preceding water washing step 26, then by line 43 to water washing step 24, and from that wash to the first water washing 22 as indicated by line 44, and then to waste or chemical recovery as indicated by line 45.
  • fresh or make-up water may be added to any one of the water washing steps as indicated by lines 46, 47, 48, 49 and that water may be sent to waste or chemical recovery from any or all of the water washing steps as indicated by lines 50, 51, 52 and 53.
  • Chlorine dioxide either in aqueous solution or in gaseous form, may be fed to each of the chlorine dioxide steps as indicated by lines 60, 61 and 62 and an aqueous solution of caustic may be fed to each of the caustic extraction steps as indicated by lines 63 and 64.
  • the novel pulp of this invention is recovered from the process, as indicated at 70, in a high yield of about to about 85 percent and at a GE. brightness of approximately 80 to 90.
  • a more preferred embodiment of the invention is a five stage process that comprises the sequential steps of chlorine dioxide treatment, caustic extraction, chlorine dioxide treatment, caustic extraction, and chlorine dioxide treatment, with a water wash between each step, and having first chlorine dioxide treatment preceded by chemical or a chemical-mechanical pretreatment.
  • FIG. 3 a block diagram of a preferred chemical-mechanical pretreatment is shown.
  • Prepared vegetable fiber chips are fed to a chemical treatment step where a prepulping treatment is given.
  • This prepulping treatment may be in the nature of a weak pulping to a high yield by a kraft, nitric acid, neutral sulfite process, or other.
  • the pre-pulping treatment the pre-pulping treatment
  • fiber chips are prepulped to a yield at least greater than 64 ercent by weight based upon the dry weight of the chips of the vegetable matter.
  • the prepulped material is refined in step 71, washed in step 72, then dewatered as indicated at 73 to prepare a combined chemically-mechanically pretreated material ready for processing in the first chlorine dioxide treatment as indicated at 21 in FIG. 2.
  • the novel process of this invention is suitable for preparing a novel pulp and paper product from any fibrous vegetable matter containing lignin.
  • the vegetable matter should have extraneous materials removed before being subjected to the process.
  • wood in the case of wood, it must be debarked in a prior operation.
  • wood will be referred to as the fibrous vegetable material; however, it should be understood that the process of the invention is applicable to all fibrous vegetable materials.
  • Debarked wood either hard or soft, may be converted into chips by a Carthage multiknife chipper or other equivalent apparatus.
  • the chips should be approximately 15 to 75 millimeters in length, 10 to 40 millimeters in width and have a thickness of 0.5 to 20 millimeters. When chemical or chemical-mechanical pretreatment is used it is preferred that chips have an approximate length and width as described and that the thickness be from about 2 to about 5 millimeters. Following chipping, prepared chips are then subjected to the pretreatment step.
  • the pretreatment step can be either mechanical, chemical or a combination of chemical and mechanical.
  • mechanical pretreatment the vegetable fiber chips are subjected to a shredding, refining, or flaking operation, such as is well known in the art, by a Pallman knife ring flaker, which by slicing reduces conventionally sized chips to thin flakes while maintaining chip length and width, or a standard disc refiner, or the equivalent.
  • the chips may be subjected to water or steam treatment prior to flaking or refining, either under vacuum or pressure, and following either flaking or refining the resulting fibers or fiber bundles should be as small as possible without significant damage to the fibers. The optimum size depends upon the flaking or refining equipment employed.
  • the vegetable fiber chips are subjected to a chemical treatment followed by a refining operation and then a water washing.
  • the chemical pretreatment results in a yield of at least about 64 percent or greater and may be a mild prepulping by a neutral sulfite, nitric acid, kraft or other known pulping process (e.g., bisulfite, acid sulfite, cold soda, soda, sodium xylene sulfonate, polysulfide).
  • a more preferred chemical pretreatment is a mild neutral sulfite prepulping under particular conditions of chemical concentrations; the heating and cooking cycles are defines infra.
  • the refining step may be performed by standard disc refiner or other equivalent apparatus and conducted to yield minimum particle size without significant fiber damage.
  • a dewatering step may be necessary prior to subjecting the pretreated fibers to the novel pulping process of this invention.
  • the preteated material enters the first chlorine dioxide treatment step.
  • the shredded mass of fiber bundles resulting from the pretreatment has a consistency of from about percent to about 50 percent by weight, based on the total weight of shredded mass and water.
  • Chlorine dioxide if used as an aqueous solution, may be fed as an approximately 1 percent by Weight aqueous solution, and depending upon the desired concentration of chlorine dioxide, which is defined infra, additional water may be added to prepare the mixture to the desired consistency. If gaseous chlorine dioxide is used, an inert diluent such as air may be necessary to prevent explosion hazards.
  • Any conventional treating tower such as is well known in the art may be used for the chlorine dioxide treatment stage and heat may be added if and as necessary. Also, additional heat may be supplied to reduce the time of contact between the shredded mass and the chlorine dioxide, which time is from about minutes to 2 hours depending upon the consistency, the temperature, and the yield of product resulting from the pretreatment step.
  • the shredded mass of fibers is permitted to remain in contact with the chlorine dioxide until the chlorine dioxide charged is substantially consumed.
  • the pH of this system at the beginning may vary from about 4.0 to about 8.0, and upon consumption of the chlorine dioxide the pH of the treated solution will be approximately 0.5 to 3.0.
  • the resulting mass is then water Washed in a conventional vacuum drum washer or the equivalent.
  • the washed material is subjected to a first alkali extraction in a conventional treating tower such as is well known in the art.
  • a first alkali extraction any water soluble caustic material may be used such as sodium hydroxide, ammonium hydroxide, sodium carbonate, ammonia gas or other or mixtures of these or others; however, an aqueous solution of sodium hydroxide is preferred.
  • the alkali application should be approximately 4 percent based on the oven dry weight of the fibrous material, and sufficient water may be added or removed to prepare an aqueous fiber mass having a consistency of from about 5 percent to about 50 percent by weight based on the total weight of shredded mass present and Water.
  • the alkali extraction should continue for at least about one-half hour at a temperature of from about 50 C. to about 75 C. with a preferred temperature of about 65 C.
  • the alkali extracted material is subjected to another water washing under substantially the same conditions as the first water wash to remove extracted materials and residual chemicals.
  • the second chlorine dioxide treatment may be carried out in a conventional treating tower such as described for the first chlorine dioxide treatment, whereby the de sired consistency of material within the tower is substantially the same for the second chlorine dioxide treatment as for the first.
  • Either gaseous chlorine dioxide or an aqueous, approximately one percent by weight, solution may be fed to this second treatment stage.
  • the pH is initially from about 4.0 to about 8.0 and ends at about 2.0; the chlorine dioxide treatment is permitted to continue until substantially all the chlorine dioxide charged to the treating stage is consumed.
  • the temperatures for the second chlorine dioxide treatment are adjusted to from about 40 C. to about 60 C. to keep contact times to a minimum of from about 30 minutes to about 4 hours to consume the chlorine dioxide charged.
  • the treated material is subjected to a third water washing under substantially the same conditions as the first and second water washings.
  • a second alkali extraction is conducted, followed by a water wash under substantially the same conditions as the first alkali extraction and wash.
  • the washed material at this stage in the process may be screened, if desired, to remove any shives of fibrous material which may remain, and these shives are discarded or returned to the first chlorine dioxide treatment stage for recycle.
  • the treated material is then subjected to a third chlorine dioxide treatment under the same conditions of consistency and chlorine dioxide concentration as the first and second chlorine dioxide treatment stages for a period of from about 2 hours to about 6 hours, depending upon the desired brightness for the product produced.
  • the temperature for this third chlorine dioxide treatment stage is from about 40 C. to about C., and following the third chlorine dioxide treatment, the treated material is subjected to a fifth and final water wash under the same conditions as the preceding water washings.
  • the total concentration of chlorine dioxide used in the multistage process is dependent upon the yield of product obtained from the pretreatment step and the desired brightness of the product resulting from the final treatment stage.
  • the total chlorine dioxide consumed in the multiple stages is from about 1.0 to about 15.0 percent by weight based on the total dry weight of fibrous material being fed to the pretreatment stage. It has been found and is preferred that the total concentration of chlorine dioxide used is from about 4.0 percent to about 13.0 percent by Weight, based upon the total weight of dry fibrous material being fed to the pretreatment stage.
  • the amount of chlorine dioxide fed to each chlorine dioxide stage is dependent upon the number of chlorine dioxide stages used and on the pretreatment yield. For any given total amount of chlorine dioxide to be used, it has been found that approximately two times the amount used in the last stage should be fed to the chlorine dioxide stage preceding the last and two times the amount used in the preceding stage fed to the next preceding stage, and so on. For example, in a three chlorine dioxide stage process, this means that approximately four-sevenths of the total chlorine dioxide will be fed to the first stage, approximately two-sevenths of the total chlorine dioxide will be fed to the second stage, and approximately oneseventh to the third stage.
  • the preferred pretreatment for the process of this invention is a chemical pretreatment, and of the chemical pretreatments available such as kraft, bisulfite, neutral sulfite, nitric acid, etc., a neutral sulfite pretreatment is preferred. And, among the neutral sulfite pretreatments available, a sodium based neutral sulfite pretreatment is preferred.
  • a standard neutral sulfite pulping treatment includes cooking fibrous vegetable material for a period of 10 to 15 minutes at about 350 F. in a concentration of approximately 10 percent sodium sulfite and approximately 3 percent sodium carbonate, chemical charges being based on the wood weight charged to the process.
  • This standard neutral sulfite pretreatment has advantages, in the process of this invention it is even more preferred that a specific and novel neutral sulfite pretreatment be used.
  • This novel chemical pretreatment includes preparing an aqueous solution of a fibrous vegetable material, which has been chipped as described previously, with a concentration of from about 5 to about 30 percent sodium sulfite and from about 3 to about 25 percent sodium carbonate to provide a sodium sulfite to sodium carbonate ratio of about 1.2 or greater. More preferred concentrations are from about 7 to about 20 percent sodium sulfite and from about 5 to about 18 percent sodium carbonate, all percentages being based upon the dry weight of the vegetable matter. A more preferred sodium sulfite to sodium carbonate ratio is from about 1.2 to about 1.5.
  • the time-temperature relationship employed is designed to give adequate impregnation of liquor into chips prior to reaching a temperature of about 300 F. This relationship is dependent upon wood species and chip size, as well as previous chip history.
  • a chemical pretreatment is performed in accordance with the described recipe, higher final yields and higher quality product are obtained as compared with other mechanical or chemical pretreatments.
  • the pulp of the present invention is chemically unique in that it has a higher degree of polymerization, a higher hemicellulose content, a higher carboxyl content, and a lower carbonyl content than pulp conventionally produced from the same wood. Due it its higher final yield as compared to conventionally bleached kraft pulp, it contains more hemicellulose. At the same time, however, the viscosity average degree of polymerization of the pulp is higher than that of conventionally bleached kraft pulp. The inescapable conclusion is that the process of the present invention degrades wood cellulose less than conventional processes in going from wood to purified pulp.
  • the carboxyl content of the pulp produced by the present invention is at least twice as great as the carboxyl content of conventionally bleached pulps and has a carboxyl number (TAPPI Standard T237su-63) greater than about 6, preferably greater than about 9, and more preferably greater than about 12, and as high as, for example, 20, and even higher.
  • the carbonyl content is only one-half to one-third as great as the carbonyl content of conventionally bleached pulp from the same wood.
  • the mechanical properties of the pulp of the present invention which are affected by its unique chemical properties are case of refining, fiber tensile strength, and ability to form fiber-fiber bonds when made into sheets and dried.
  • the pulp of the present invention consumes only one-third to one-fourth of the energy required to beat a conventionally bleached kraft pulp from the same wood mixture to the same freeness level.
  • the rate of beating of the pulp of the present invention is 4.2 times as great as the rate for the corresponding bleached kraft pulp when prepared from a northern hardwood mixture and 3 times as great using the southern hardwood mixture. Since the time required to beat a pulp is directly proportional to the energy required to beat that pulp, the pulp of the present invention exhibits a substantial savings in refining energy input required to reach a given freeness level.
  • the rate of mechanical refining (ml. Canadian St. per minute of beating carried out according to TAPPI Standard T200ts66) can be greater than about 15, preferably greater than about 20, more preferably greater than about 25, and may extend up to, for example, 50 and even higher.
  • the pulp of the present invention is formed into paper on a paper machine, more rapid drainage, increased ability to retain fibers, increased wet web strength, and increased drying rate are observed relative to conventional pulp prepared from the same wood.
  • Strips of handsheets from the pulp of the present invention possess superior tensile strength and tear strength when compared to conventionally bleached kraft pulp from the same wood mixture. This is unusual since pulps with higher tensile strength usually possess lower tear strength.
  • the fact that the present pulp possesses both a superior tear strength and superior tensile strength indicates another unique physical property of the pulp of this invention; it also possesses superior individual fiber tensile strength.
  • the properties of these pulps relate directly to papers made from them.
  • Machine made paper from pulp of the present invention produces higher tensile, tear, burst, fold pick and delami-nation strengths.
  • the grease proofness (TAPPI Standard T454ts-66) of the paper of this invention can be greater than about 500 sec., preferably greater than about 1000 sec., and can extend up to, for example, 1800 sec.
  • tensile strength (TAPPI Standard T404ts66) for paper from hardwood pulp can be greater than about percent, preferably greater than about percent, more preferably greater than about percent and may extend up to, for example, 200 percent and even higher, and for paper from softwood pulp it can be greater than about 120 percent, preferably greater than about percent, more preferably greater than about percent, and may extend up to, for example, 250 percent and even higher;
  • bursting strength (TAPPI Standard T403ts63) for paper from hardwood pulp can be greater than about 140 percent, preferably greater than about 160 percent, more preferably greater than about percent, and may extend up to, for example, 250 percent and even higher, and for paper from softwood pulp it can be greater than about 160 percent, preferably greater than about 190 percent, more preferably greater than about 230 percent, and may extend up to, for example, 300 percent and even higher;
  • tearing resistance (TAPPI Standard T4l4ts-65) for paper from hardwood pulp can be greater than about 160 percent, preferably greater than about 220 percent
  • R carbohydrate retention factor grams carbohydrate retained grams carbohydrate initially present Optimum condtions result with a high value of E, while maintaining an R value as close to unity as possible. By comparison, a bleached hardwood kraft pulp would have an R value of approximately 0.55.
  • the table below shows the results of these experiments for a single chlorine dioxide stage, a single stage followed by an extraction, and a three-stage sequence. It will be noted that the inclusion of the extraction stage (second case) more than doubles the eificiency while not greatly reducing the retention or selectivity factor. Since the product following any extraction stage is very dark, a final chlorine dioxide stage is required to produce a bleached product. The high E and relatively high R values are maintained through this second chlorine dioxide stage, demonstrating the superiority of the multistage approach.
  • the resultant product is not of as high a brightness as it is possible to achieve.
  • the resulting pulp contains some shives of fiber bundles.
  • Use of more chlorine dioxide in each of the two stages as well as use of a more severe extraction stage improves results. However, this leads to an increase in chlorine dioxide consumption and a decrease in R.
  • the preferred method of producing a bleached pulp with a negligible quantity of shives is conducted by expanding the sequence to five stages of intermittent chlorine dioxide-extraction (with intermediate washing). The additional stages give the caustic an additional opportunity to soften and disperse the fiber bundles, and also to remove further alkali-soluble lignin materials and thereby reduce the overall chlorine dioxide consumption.
  • Representative samples of the resultant pretreated material were subjected to various chlorine dioxide extraction sequences. The following conditions were held constant during these tests.
  • ammonium hydroxide extraction even at the higher level of chemical application, is less eflicient in lignin extraction. Also, ammonium hydroxide ofi'ers no advantage in carbonhydrate preservation.
  • FIGS. 4 and 5 show that yield losses and brightness are relatively little aflfected by temperature. However, while yield loss is approximately proportional to alkali applied, there is little advantage in either brightness increase or rejects reduction in using more than about 4 percent sodium hydroxide at 12 percent consistency. Therefore, to conserve yield while achieving maximum brightness and minimum rejects, about 4 percent applied caustic is employed at 12 percent consistency.
  • FIG. 6 clearly shows that a higher temperature (65 C.) is advantageous in reducing rejects. Since this does not adversely affect yield, preferred temperature conditions for extraction are above ambient, in the vicinity of 65 C.
  • EXAMPLE V To show the preferred range of sodium base neutral sulfite pretreatment yield, a series of sodium base neutral sulfite pretreatments was carried out. In all cases, sufiicient (and constant between runs) liquor impregnation of the southern hardwood chips was allowed before the pretreatment temperature was raised to its maximum of 335 F. Following the chemical pretreatment, the hardwood materials were refined in an eight-inch laboratory disc refiner and thoroughly washed. The materials were then pulped and bleached to G.E. brightness (TAPP-I Standard T 217m48) by the preferred five-stage chlorine dioxide-caustic extraction sequence, using the total amounts of chlorine dioxide corresponding to the level of pretreatment yield involved and shown in Example IX. The pretreatment yield range covered was 61 percent to 86 percent.
  • the yield data, strength data of standard laboratory handsheets, and some data on the degree of polymerization (DR) of the final bleached pulp is summarized in the following table.
  • Runs 1 and 2 at equal pretreatment yield, show the efiect of variations in applied chemicals.
  • FIG. 8 shows the pretreatment yield-chlorine dioxide consumption relationship for neutral sulfite pretreatment, with the no-chemical pretreatment point corresponding to 100 percent pretreatment yield.
  • the neutral sulfite line is followed until a pretreatment yield of 95 percent is approached; at this point the consumption rises rapidly from this line and passes through the no-chemical pretreatment point.
  • a disproportionately large amount of chlorine dioxide is consumed. This is, of course, very undesirable.
  • FIG. 7 shows a parallel behavior for bleached yields. At pretreatment yields above about 95 percent, the bleached yield actually decreases to the point corresponding to mechanical pretreatment only. Since maximum yield is desirable, this decrease is undesirable.
  • Example IX Further reason for maintaining pretreatment yield below 95 percent is found in Example IX, in which it is Shown that 100 percent pretreatment yield produces inferior paper strength properties as compared with papers in the below 95 percent pretreatment yield range.
  • EXAMPLE VI To demonstrate the preferred conditions for the sodium base neutral sulfite pretreatment, it is shown below that proper pretreatment liquor impregnation of the chips prior to heating is necessary to maximize handsheet strength and minimize fiber bundle or shive content. It is also shown that proper ratio of pretreatment chemicals is necessary to provide maximum strength and ease of pulping and bleaching with the subsequent chlorine dioxide-caustic sequence.
  • Runs were made using two extremes of liquor impregnation prior to chemical pretreatment, and with a range of ratios of sodium sulfite to sodium carbonate in the pretreatment liquor. In all cases sufficient pretreatment chemical was applied so that the final liquor pH was above 7. If allowed to drop below this value, a weak pulp resulted.
  • the raw material was a southern hardwood chip mixture.
  • the materials produced were refined under constant conditions in a laboratory eight-inch disc refiner, thoroughly water washed, and subjected to the five-stage chlorine dioxidecaustic sequence for pulping and bleaching to 80 GE. brightness (TAPPI Standard T 2l7m-48). The total chlorine dioxide required to achieve this brightness was determined together with standard handsheet physical tests on the bleached pulp.
  • pulping chemical chlorine dioxide
  • pulp handsheet strengths results when the sulfite/carbonate ratio is reduced from about five to slightly more than one.
  • Runs 3 and 4 show the effect of still further reduction in this base ratio from 1.2 to 1.0.
  • a very significant decrease in pulp handsheet strentghs results, along with a large increase (about 25 percent based on the normal chemical application) in chlorine dioxide consumption.
  • a sulfite/carbonate ratio of slightly above unit it is critical that this ratio not be allowed to drop below about 1.2 because of detrimental effects on both pulp physical properties and pulping chemical consumption.
  • Runs 1, 3 and 5 show the importance of adequate pretreatment liquor impregnation of the chipped raw material. Since the chemical ratio of Run 5 is intermediate between those of Runs 1 and 3, the observed marked decrease in handsheet physical properties is attributable to the lack of adequate chip impregnation. Optimum impregnation conditions depend upon the type (wood species) and chip dimensions of the raw material. Sufiicient pretreatment chemical must be added to maintain the pH at 7 or above during the pretreatment.
  • the ratio of sodium sulfite to sodium carbonate applied should be held in the vicinity of about 1.5 for highest pulp strength. Higher values result in reduced strengths; values below about 1.2 give weaker pulps and increased pulping chemical (chlorine dioxide) consumption.
  • Adequate pretreatment liquor penetration into the raw material must be achieved, or strength properties suffer and shive content increases. Optimum conditions depend upon raw material structure and particle dimensions.
  • cent of the total chlorine dioxide requirement on an equivalent oxidant basis this maximum corresponds to a weight proportion of about 50 percent chlorine and 50 percent chlorine dioxide.
  • the three chemical-mechanical pretreatments were achieved using the chemical conditions shown below using mixed southern hardwood chips as raw material. In all cases, the chemical pretreatment was followed by refining in a laboratory eight-inch disc refiner, thorough washing, and pulping and bleaching using the chlorine dioxidecaustic-chlorine dioxide-caustic-chlorine dioxide treatment sequence. Conditions and results are in the table below.
  • nitric acid pretreatment results in both lower bleached yield and lower handsheet strength, indicating excessive carbohydrate degradation during this pretreatment.
  • Sodium base neutral sulfite produces a stronger pulp than ammonia base pretreatment. Also, with the ammonia base pretreatment it is more dilficult to delignify and bleach, and the pulp contains somewhat more shives and fiber bundles.
  • gfil efiieutral sulfite pretreatment cycle for both sodium and ammonia base involved 30 min. to and 60 min. at 273 F. plus 30 min. to and min.
  • the raw material was a mixture of southern hardwood chips (approximately one-third oak, one-third yellow poplar, and one-third gum).
  • chemical pretreatments kraft and neutral sulfite
  • suflicient time for liquor impregnation was allowed prior to heating to maximum temperature.
  • the chemically pretreated material (and the hardwood chips following presteaming in the case of mechanical pretreatment only) was then refined in an eight-inch laboratory disc refiner to give a starting material for the chlorine dioxide pulping/bleaching sequence. Pretreatment was analyzed through the following:
  • Pretreatment S (pretreat- Pretreatment yield ment only)
  • TAPPI Standard T404 ts-66 2 TAPPI Standard T404 ts-66. 3 TAPPI Standard T403 ts-63. 4 TAPPI Standard T414 ts-65. 5 TAPPI Standard T227 m-58.
  • the sodium base neutral sulfite pretreatment is preferred over either high-yield kraft or mechanical pretreatment, since it results in higher final bleached yield, lower chlorine dioxide consumption, and higher pulp handsheet strengths.
  • EXAMPLE XI To demonstrate the superiority of the sodium base neutral sulfite-chlorine dioxide sequence relative to conventionally bleached kraft pulps, the below tests were conducted. Previous examples have demonstrated the superiority of the product of the sodium base neutral sulfite-chlorine dioxide process relative to conventionally bleached neutral sulfite as well as relative to pretreatment-chlorine dioxide sequence pulps in which the pretreatment is any of the following: mechanical, ammonia-base neutral sulfite, high-yield kraft, and nitric acid.
  • pulp samples were prepared using two processes: the sodium base neutral sulfite pretreatmentchlorine dioxide pulping sequence of the present invention and a conventionally pulped and bleached kraft pulp. These pulps were refined to 300 degrees Canadian Standard Freeness (TAPPI Standard T227 m-58) and formed into paper on a small twelve-inch paper machine, so that the results would be more indicative of the properties of machine-made papers.
  • TAPPI Standard T227 m-58 The physical and surface smoothness properties of these two papers are compared in the following tables:
  • MD and CD refer to machine direction and cross-machine direction eet properties.
  • Gurley porosity is the time interval required to pass a constant volume of air through the sheet, thus high values indicate low porosity.
  • Bekk smoothness is the time required to leak a constant volume of air between the sheet and a polished glass surface, thus higher values indicate greater sheet smoothness.
  • Shefliold smoothness is the rate at which air leaks between two rings which are in contact with the sheet. Thus, high values indicate low smoothness.
  • Zero-span Pulp value, percent 1 Conventional bleached kraft 89 Neutral sulfite-chlorine dioxide TAPPI Standard T231 Sill-60. Values expressed as percent calculated as:
  • EXAMPLE XII To demonstrate that, in addition to the superior properties of the pulp of the present invention when made into laboratory handsheets or paper on a paper machine, the pulp exhibits certain unique properties related to its processing before and during the papermaking operation, such as great ease of refining, increased ease of drainage during paper formation, ability to retain fillers more efficient- 1y, superior wet web strength on the paper machine, and increased ease of paper machine drying, the following comparisons were made.
  • Wood Process Southern hard- Conventionally bleached 650 woods. kraft.
  • Do Neutral sulfite-chlorine 0 740 dioxide sequence Do Cinfferionally bleached 14 600 ra t. Do Neutral sulfite-chlorine 8 600 dioxide sequence. Do Cinvfentionally bleached 25 500 ra t. Do Neutral sulfite-chlorine 11 500 dioxide sequence. Do Cinvfetntionally bleached 34 400 ra Do Neutral sulfite-chlorine 14 400 dioxide sequence. Do C l gnvfefintionally bleached 41 300 19. Do Neutral sulfite-chlorine 15 300 dioxide sequence. Northern hard- Conventionally bleached 0 600 woods. krait.
  • Do Neutral sulfite-chlorine 0 660 dioxide sequence Do ognvfetntionally bleached 0 600 ra Do Neutral sulfite-chlorine 600 dioxide sequence. Do conventionally bleached 36 500 kraft. Do Neutral sulfite-chlorine 500 dioxide sequence. Do Ctlinventiona-lly bleached 59 400 raft. Do Neutral sulfite-chlorine 14 400 dioxide sequence. Do Cinvfegitionally bleached 80 300 ra Do Neutral sulfite-chlorine 18 300 dioxide sequence.

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US797209A 1969-02-06 1969-02-06 Pretreatment of vegetable matter and delignification of the refined matter with chloring dioxide Expired - Lifetime US3591451A (en)

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3919041A (en) * 1969-02-06 1975-11-11 Ethyl Corp Multi-stage chlorine dioxide delignification of wood pulp
US6569285B2 (en) * 2000-02-09 2003-05-27 Akzo Nobel N.V. Process for gas phase pretreating of lignocellulosic containing material
US20040244925A1 (en) * 2003-06-03 2004-12-09 David Tarasenko Method for producing pulp and lignin
AU779711B2 (en) * 2000-02-09 2005-02-10 Akzo Nobel N.V. Pulping process
WO2012007642A1 (en) * 2010-07-13 2012-01-19 Olli Joutsimo Improved method of processing chemical pulp
US20130000855A1 (en) * 2009-11-24 2013-01-03 Upm-Kymmene Corporation Method for manufacturing nanofibrillated cellulose pulp and use of the pulp in paper manufacturing or in nanofibrillated cellulose composites

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3919041A (en) * 1969-02-06 1975-11-11 Ethyl Corp Multi-stage chlorine dioxide delignification of wood pulp
US6569285B2 (en) * 2000-02-09 2003-05-27 Akzo Nobel N.V. Process for gas phase pretreating of lignocellulosic containing material
US6752904B2 (en) 2000-02-09 2004-06-22 Akzo Nobel N.V. Process for removal of lignin from lignocellulosic material
AU779711B2 (en) * 2000-02-09 2005-02-10 Akzo Nobel N.V. Pulping process
US20040244925A1 (en) * 2003-06-03 2004-12-09 David Tarasenko Method for producing pulp and lignin
US20060169430A1 (en) * 2003-06-03 2006-08-03 Pacific Pulp Resources Inc. Method for producing pulp and lignin
US20130000855A1 (en) * 2009-11-24 2013-01-03 Upm-Kymmene Corporation Method for manufacturing nanofibrillated cellulose pulp and use of the pulp in paper manufacturing or in nanofibrillated cellulose composites
WO2012007642A1 (en) * 2010-07-13 2012-01-19 Olli Joutsimo Improved method of processing chemical pulp
US9139955B2 (en) 2010-07-13 2015-09-22 Olli Joutsimo Method of processing chemical pulp

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DE2005526A1 (de) 1970-10-01
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DE2005526C3 (de) 1975-11-06
DE2064963A1 (de) 1971-11-04

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